1. Field of the Invention
The present invention relates to a cooling fan, and more particularly relates to a cooling fan having good lubricating characteristics.
2. Description of Related Art
With the continuing development of the electronic technology, electronic packages such as CPUs (central processing units) are generating more and more heat that requires immediate dissipation. Cooling fans are commonly used in combination with heat sinks for cooling the CPUs. Cooling fan performance mostly depends on performance characteristics of a bearing used thereby.
Referring to FIG. 6, a conventional cooling fan includes a rotor 1 having a shaft 2 extending downwardly from a central portion of the rotor 1, a bearing 3 defining an inner hole for receiving the shaft 2 therein, and a frame 4. A central tube 5 extends upwardly from a middle portion of the frame 4 and defines a through hole 7 therein. The bearing 3 impregnated with lubricant oil is secured in the through hole 7 of the central tube 5 to rotatably support the rotor 1. An oil retaining ring 6 is mounted around the shaft 2 and located above a top end of the bearing 3 when the cooling fan is assembled. A gap is defined between a circumferential surface of the oil retaining ring 6 and an inner circumference of a top end of the central tube 5. During operation of the cooling fan, the oil originating from the bearing 3 passes out through the gap and is lost. Lubrication of the bearing 3 is thus gradually diminished. The friction between the shaft 2 and the bearing 3 increases, resulting in noise or malfunctioning. Finally the performance of the cooling fan is reduced, and the life-span is shortened in result.
What is needed, therefore, is a cooling fan which can reduce or eliminate lubricant oil loss.